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Mz6 writes "Back in January Slashdot reported about the Stardust probe and its capture of particles from the tail of Wild 2 (pronounced 'Vilt 2'). You might also remember about how it snapped 72 images of the comet and sent them back to JPL. Well, after a detailed analysis of the comet Wild 2 and building upon preliminary analysis in March, it has left astronomers at JPL astounded at an object that has no known peers in the solar system. The comet has towering protrusions and steep-walled craters that seem to defy gravity, more than a dozen jets of material shoot out from its insides, dust swirls around the comet in unexpectedly dense pockets, and boasts 2 large 'footprints', aptly named Left and Right."

Ok... Well when I submitted this story I forgot to include links to the Stardust Website [nasa.gov], Wild 2 Photos [nasa.gov], and some interesting Wild 2 Stereo Photos [nasa.gov] (2.0 MB). Best of all.. there's minimal reading, just pretty pictures. Enjoy:)

Sounds to me like this is just an inter-stellar traveller from afar making his daily rounds. I'm going to laugh if we try to land a probe on a comet and some windshield wiper-like apparatus fires up and sweeps the probe off.

That sounds like something from the Hitchhikers Guide to the Galaxy. Actually I wouldn't be surprised if this comet is making its rounds looking for a new hyperspace bypass. Pack your things, we're all going to be demolished next Thursday...

I wonder if it's just a coincidence as this is how my morning started:
"You wake up. The room is spinning very gently round your head. Or at least it would be if you could see it which you can't..."

Hm, seems to me that this is your interstellar traveller: King Ghidora [internationalhero.co.uk]. He is also known as "The God from Space", "The Strongest Foe", "The God of Mass Extinction", "The Great Devil That Comes From the Sky", "The Thousand Year Dragon King" and "Guardian God of the Heavens" in his various incarnations, both good and evil.

December 20th is his fortieth birthday, and Toho isn't throwing him a party. (Well, they did in 2001, but he wants another one.) So he has been showing off, with close asteroid flybys, f

The comma follows the word "comet." It is traditional to assume that a phrase, which follows a comma, refers to the word immediately preceding the comma. Hence the author means that the comet is 3 miles wide - which is true. The editor did not consider this ambiguous, as anyone with a basic understanding of English grammar should follow the author's intent. Perhaps the moderators have marked this as funny because they think you are being ironic. That or they believe your ignorance

Craters on Wild 2, presumably caused by run-ins with smaller objects, are strangely free of the powder, rocks and other debris commonly seen in impact craters on other bodies. Brownlee thinks this is because the comet is a bit like hard, frozen dirt that takes a hit but is brittle, so material flies out.

And because the comet is so small, the material does not fall back.

"There's almost no gravity at the surface," Brownlee said. "If you were standing on [the surface], you could jump into orbit."

The thing is, that doesn't seem right. You shouldn't be able to "jump into orbit" anywhere (barring atmospheric braking, a change of mass, additional thrust applied, etc, to change your velocity). Your path will either intersect the object you're jumping from, or break its escape velocity. Perhaps this is different for irregularly shaped bodies with irregular gravitational fields, but good luck trying to establish a stable orbit there through "jumping"....

Now, you *could* "run into orbit", assuming you can get the traction to do so, on a perfectly smooth low gravity atmosphere-less body - you run up to orbital velocity, then curl your body up, and you'll orbit at the altitude of your center of mass. But, if you were to have any significant "jumping" component, you'll likely make yourself intersect the body you're trying to orbit.

Also, you could jump up and throw a rock and enter orbit that way. However, in the case that you're dealing with a uniform graviational field around a perfect sphere, and the rock that you throw has the same mass as you, you'll hit it on the other side;)

There are a variety of ways of jumping; only some involve jumping from a standstill. Also your analysis doesn't mention the comet's rotation. If you jump straight up, your orbit will be elliptical rather than a 'straight line'. I don't have time to prove that the angular component of velocity is enough to prevent collision. Maybe after I'm done teaching for the day....

You'll still intersect, so long as you aren't moving along the surface, assuming a uniform gravitational field (I don't know about irregular fields). It essentially doesn't matter what angle your jump is at - it doesn't have to be straight up for you to intersect. The only way you could "jump" into orbit is if you angled your jump the same way you'd angle a run: almost perfectly parallel to the surface of the object, and then tucking your legs and arms in. If an object can't deform itself as such, in suc

Yes. Instead of doing a lot of orbital calculations, I found it much easier to do a reverse time analysis. Obviously any orbit that brings an object to the surface of a (rotating) spherically symmetric mass with any arbitrary velocity is an elliptical orbit that intersects the surface of the mass periodically or a hyperbolic orbit. If you do jump with something more than escape velocity, you will get out of the asteroids gravity well. But you'll still be in orbit... around the sun.

of course you can jump into orbit, and out of orbit. you seem to be assuming you can run faster than you can jump. in low-gravity, running is very difficult, jumping is easy. and in low-gravity, escape velocity is very low.

Nope. Your path will either escape or intersect the body that you jumped from (given the criteria described above, such as uniform spherical gravity field). There are a number of pages on the internet which describe why; want a link? And, as I mentioned, running *is* hard in low gravity, that is why I made it conditional on being able to get enough traction.

I know it's a dirty snowball but I'm really curious about how much is water, how much is ammonia and other stuff and how much is rock. In the crazy proto-science of terraforming, comets are earmarked for use as atmosphere builders. Depending on the general makeup of the objects, it could drastically change the models for terraforming Mars, Venus and other places.

I recently saw a programme that claimed that about 350,000 tonnes of materal from comets fall to earth each day. Most of this is water, hydrocarbons, ammonia, carbon and other stuff useful for creating life. I can't find any other source to back up the number, but most give a value of thousands of tonnes per year. Assuming that quantities of a similar magnitude a falling onto Mars' surface I'd be suprised if life hasn't been/isn't doing a bit of small scale terraforming already.

Assuming that quantities of a similar magnitude a falling onto Mars' surface I'd be suprised if life hasn't been/isn't doing a bit of small scale terraforming already.
That would require there to be life on Mars (or the comets), though, wouldn't it? (Which, of course, there might be, I'm not saying there isn't.... *backs away from the angry "Life on Mars" supporters*)

It is not a "dirty snowball". See James McCanney Science [jmccanneyscience.com]. You will need to read his two books "Planet X, Comets and Earth Changes" and "Atlantis to Tesla - The Kolbrin Connection" in that order.

I think, instead of trying to exactly and respectfully pronounce names correctly in their original language, that each country, or language group, pronounce it phonetically in their own language.

All this overcorrectness could possibly give rise to errors, such as a member of the general public thinking there are two comets, after hearing about "Viltzwei" on the radio and reading about "Wild 2" in the papers.

Actually Star Trek uses the Universal Translator, so if you overlook a fwe (ok, maybe more)discrepencies, you can assume that everyone's speaking in their own language.
Stargate SG1 on the otherhand. Do they have an excuse? They seem to be able to communicate with almost everyone they meet. The residents on other planets come from Earth, but thousands of years ago and from different parts of the planet.
Do the SG teams have UCs as well?

Thank you for illustrating my point with such precision. I suggest people in each locality pronounce it as they read it, for the sake of simplicity & layman understanding -- you insist they must educate themselves to your level and become expert linguists.

But while your nose-in-the-air approach proves your intellectual superiority over them, it is also snobbish and counterproductive to the dissemination of scientific knowledge to the masses.

Do we pronounce "2" as "two", as what the Arabic word for "two" looks like, as "one zero", or as the Roman "II"? Rather than Arabic, perhaps we should have the written word in Babylonian, or what preceded the Arabic: the Brahmi "=" or Nagari "2" [st-and.ac.uk].

I mean, we already know they're pieces of rock, ice and other minerals, in a near future, what possibilities could we have to extract those rare metals or compounds...? (forget any mention of Armaggedon and Deep Impact)

Comets do have gravity. Although it's not anyhting in comparison to some of the other celestial objects, as small as some are (or even as large as others are) they do have more gravity than you might think.

If you browse around the Stardust website a bit more you will find a report that scientist were disappointed in the mission becuase it grabbed a lot less material then they had at first thought. It's still on par to land in 2006, in a very remote part of Utah -- the desert.

The pictures are quite amazing. It is very puzzling why so small an icy body can have flattened crater floors. It does not take much gravity toallow warmed ice to viscuoously relax apparently.When I look at the images of those amazing spireson the comet limb. I can't help but think aboutthe descriptions of Comet Haley's surface inArthur C. Clarke's 2061. That guy has spooky prescience.

"Only two other comets have been seen up close, but both appeared fairly smooth and were nowhere near so heavily cratered."

Well with such a HUGE sample pool, I can see how they're able to make such firm analysis of this meteor! I mean, really - both the others they've seen up close didn't look at this one, so clearly this one is completely unique in the solar system!

Perhaps I should have explained more... I've seen various algorithms for shape from shading - some are quiet accurate. Given the multiple (and stereoscopic) photographs from different angles, surely it would be possible to construct a 3D model?

From the NYT article: "Flying through the dust around Wild 2, the spacecraft gathered thousands of particles that are now being returned to Earth for closer investigation. A capsule holding the exotic cargo is to make a soft landing in the Utah desert in January 2006."

You might try reading the rest of the article before you go all asshat. This is the comet's first trip thru the inner solar system.

"In 1974 it had a close encounter with Jupiter and was thrown onto a new orbit that brings it closer to the Sun. A comet loses material when it approaches the Sun, as solar radiation causes ice from its surface to "sublimate" into space, carring dust and larger particles with it. The process creates a cloud of material that reflects sunlight and creates the familiar head of a comet (scientists call it a coma) and sometimes a tail."

Ever hear of long eccentric orbits that bring comets nearer the sun for brief periods? That would be the simple explanation, even if you didn't RTFAs.

But if you do RTFAs, you learn that Wild 2 had a recent close encounter with Jupiter that substantially changed its orbit, so it's likely that it has received substantially more solar heating in recent decades.

yes, but if you read the article, you would have seen that "In 1974 it had a close encounter with Jupiter and was thrown onto a new orbit that brings it closer to the Sun. A comet loses material when it approaches the Sun, as solar radiation causes ice from its surface to "sublimate" into space" So in no way could you say that the loss is "uniform" before 1974, it would have lost damn little of it's mass

It seems you are the one doing the crap science. If you would have read the article, you would have noticed it said, "In 1974 it had a close encounter with Jupiter and was thrown onto a new orbit that brings it closer to the Sun. A comet loses material when it approaches the Sun, as solar radiation causes ice from its surface to "sublimate" into space, carring dust and larger particles with it. The process creates a cloud of material that reflects sunlight and creates the familiar head of a comet (scientist